The present invention relates generally to the production of electrical steel core laminations and more particularly to a method and apparatus for doing so.
Electrical steel core laminations are used in the cores of rotors and stators for electric motors and in the cores of small transformers, for example. These laminations are stamped by a manufacturer thereof from cold rolled steel strip which is usually subjected to a decarburizing anneal either before the stamping operation, by the steel maker, or after the stamping operation, by the manufacturer of the laminations. The considerations involved in the composition and processing of the cold rolled steel strip before stamping, in the decarburization thereof and in the stamping, annealing and other operations performed by either the steel maker or the manufacturer of the laminations, are discussed in some detail in Rastogi U.S. Pat. No. 4,390,378 and in Rastogi, et al. U.S. Pat. No. 4,601,766, and the disclosures of both of these patents are incorporated herein by reference.
It is usually more desirable for the decarburizing anneal to be performed by the steel maker rather than by the lamination manufacturer. In those situations where the manufacturer of the lamination does not perform a decarburizing anneal after stamping the lamination, another type of anneal is usually performed to relieve the stresses resulting from the stamping operation and to enhance the magnetic properties of the lamination.
All anneals performed by the manufacturer of the lamination, whether a decarburizing anneal or a stress relieving anneal, are usually conducted at a location remote from the stamping press at which the lamination was made. Typically, the lamination is conducted away from the stamping press through a downwardly inclined chute having an upper, entry end located adjacent the stamping press to receive a lamination after it has been stamped on the press. The chute is typically trough-shaped, open at the top, and the chute communicates at its lower, exit end with a conveyor or other material handling device for transporting the laminations from the exit end of the chute to an annealing furnace. The laminations move through the downwardly inclined chute at least partially under the urging of gravity.
The annealing furnace may be gas fired, for example, or an induction furnace may be employed.
Koshiishi, et al. U.S. Pat. No. 4,602,969 discloses a method for subjecting core blanks (laminations) to a stress relieving anneal after the core blanks have undergone blanking, presumably at a stamping press. The core blanks are transported by a conveyor, presumably from the stamping press, to annealing equipment wherein the core blanks are initially elevated upwardly through a vertical tube containing induction heating coils. At the top of the induction heating tube, the core blanks are discharged onto another conveyor which transports the core blanks through a soaking heating chamber followed by a cooling chamber. In Koshiishi, et al. the core blanks are annealed after they have been conveyed away from the stamping press to an annealing furnace remote from the press, and complicated apparatuses are employed to elevate the stamped laminations through the vertically disposed induction heating arrangement, and then to convey the core blanks through additional heat treating equipment. The core blanks are subjected to loading and unloading operations at an annealing furnace, as well as other material handling operations, separate and discrete from those employed to conduct the core blanks away from the stamping press.